                1. Field of the Invention        
The present invention relates to a device for collecting solar energy. In particular it relates to a device comprising at least one dense suspension of particles fluidized by a gas.
2. Description of Related Art
Viable exploitation of solar energy requires some of the heat produced during daylight hours to be stored so that it can be recovered at times of demand, or at the very least used to ensure continuity of supply during cloudy periods.
For this storage of heat, it is known to use the same fluid employed as the heat transfer fluid (for example a molten salt).
It is also possible to use steam as the heat transfer fluid. However, this solution has the drawback of a limited operating temperature.
It is also possible to use, as the heat transfer fluid, synthetic oils or mixtures of molten salts, especially mixtures of potassium nitrate and sodium nitrate. Using synthetic oils or molten salts has the drawback of being dangerous, these substances also being highly toxic.
Thus, it was conceived to use suspensions of solid particles to absorb the solar radiation, but this solution has proven to be unsatisfactory, especially because of the low density obtained for the suspensions and of the high energy losses related to compression of the air required for producing the suspension.